Buried pipe insulation steel jacket Overview: the transport medium, operating pipe, foam insulation, polyethylene plastic outer sheath tube, contact is made through the device sequentially outward. Steel jacket pipe insulation steel jacket pipe insulation 1.1 First layer: steel layer based on job planning and customer demand is generally used in seamless (GB8163-87) spiral pipe (GB9711-88; SY / T5038-92) and the straight stitch pipe (GB3092-93). After the cast steel look through leading technology wan rust treatment, rust steel grades up to GB8923-1988 specification Sa2 level, look roughness up GB6060.5-88 specification R = 12.5 m. 1.2 Second layer: polyurethane foam insulation with high-pressure steel pipe machine in the cavity between the outer protective layer of write-once made of rigid polyurethane foam liquid. Commonly known as "pipe-in-pipe foam technology." First, the effect of water, the second is the insulation, the third is to support the weight of the heat network. When the delivery medium temperature: -50 ℃ -120 ℃, the selection anji isocyanurate rigid polyethylene foam insulation do. 1.3 The third layer: high-density polyethylene protective layer thickness must be preformed black (yellow) plastic pipe, the effect of one maintenance polyurethane insulation layer from mechanical hard object damage, and second, anticorrosion and waterproof. 2 Parameter Standard: OD mm 238 mm 3.5 thickness weight Kg 2.475 permissible error corresponding to the pipe diameter mm ± 0.28 mm 159 mm 37 corresponds to the thickness of the insulation layer corresponding to the sleeve mm 245 3 Features: 1, decrease the project cost. 2, low heat loss and save energy. 3, anti-corrosion, insulation, the use of long life. 4, small footprint, fast construction and maintenance of an enabling environment. 5, safety.